VGLL1 peptide-specific CTLs isolated and expanded from PBMCs (peripheral blood mononuclear cells) of a PDAC patient robustly killed autologous tumor cells, in addition to recognizing a panel of allogeneic HLA-A*0101-positive PDAC, ovarian, gastric, bladder, lung, and basal-like breast cancer cell lines. This evidence concerns the gene VGLL1 and breast cancer.